The accordion folded paper air filters used for cleaning the air supplied to internal combustion engines become clogged by the accumulation of dust and other matter removed from the air. It has been found to be practical and highly economical to clean the filters on large engines so that they may be used a number of times instead of being discarded after becoming clogged. Apparatus has been provided for the quick and effective cleaning of such filters and, by way of example, one form of such apparatus is disclosed in U.S. Pat. No. 3,688,780, granted Sept. 5, 1972, to Herbert L. Everroad. In order to avoid the loss of time and expense in the cleaning of filters having holes therein rendering them ineffective, it has become a regular practice to inspect the filters for imperfections or flaws to determine their effectiveness for reuse before subjecting them to the cleaning process. One method which has been used for such inspection is to brush off any heavy deposits of dust or other material and to position a bright light on one side of the filter and to watch on the other side for any light penetration; the light is moved about until a defect is found or until the entire filter has been inspected. While this method has been effective for detecting a great many defective filters, it has not been fully effective for detecting very small but disabling holes in many filters. Accordingly, it is an object of the present invention to provide an improved method and apparatus employing light for the detection of holes in porous media including air filters and the like.
It is another object of this invention to provide an improved apparatus and method for detecting holes in filters and the like which is quick and highly effective for the detection of holes including extremely small holes.
It is another object of this invention to provide an improved method and apparatus utilizing light for the detecting of holes in paper filters and the like with increased speed and effectiveness.
It is a further object of this invention to provide an improved method and apparatus for detecting holes or imperfect seals in air filters and the like as manufactured or after use.